Identification of a novel family of nonclassic yeast phosphatidylinositol transfer proteins whose function modulates phospholipase D activity and sec14p-independent cell growth
Identification of a novel family of nonclassic yeast phosphatidylinositol transfer proteins whose function modulates phospholipase D activity and sec14p-independent cell growth
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DOI：
10.1091/mbc.11.6.1989
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发表时间：
2000-06-01
影响因子：
3.3
通讯作者：
Bankaitis, VA
中科院分区：
文献类型：
--
作者：
Li, XM;Routt, SM;Bankaitis, VA
酵母磷脂酰肌醇转移蛋白（Sec14p）对高尔基功能和细胞活力至关重要。我们现在报道了5个酵母SFH （sec14同源）蛋白的特性，它们与Sec14p具有24-65%的同源性。我们发现，Sfh1p与Sec14p具有64%的初级序列同源性，但在体内和体外都不具有作为Sec14p的功能。然而，与Sec14p具有低一级序列相似性的SFH蛋白（即Sfh2p， Sfh3p， Sfh4p和Sfh5p）代表了新型磷脂酰肌醇转移蛋白（PITPs），其在体外表现出磷脂酰肌醇-但不具有磷脂酰胆碱转移活性。此外，Sfh2p、Sfh4p或Sfh5p的表达增加以磷脂酶D （PLD）敏感的方式挽救了sec14相关的生长和分泌缺陷。一些独立的证据进一步表明，SFH pitp是有效激活营养细胞PLD所必需的。其中包括在不依赖sec14p的细胞生长中对SFH蛋白的集体需求，以及在sec14p缺陷细胞中对PLD的最佳激活。与这些发现一致，Sfh2p与内体腔室中的PLD共定位。这些数据表明，SFH基因产物与“旁路-Sec14p”突变和PLD合作，通过复杂的相互作用，酵母可以适应Sec14p基本功能的丧失。这些发现扩大了酵母中PITP功能的生理范围，并首次在体内证明了特定PITP在刺激PLD激活中的作用。
Yeast phosyhatidylinositol transfer protein (Sec14p) is essential for Golgi function and cell viability. We now report a characterization of five yeast SFH (Sec Fourteen Homologue) proteins that share 24-65%: primary sequence identity with Sec14p. We show that Sfh1p, which shares 64% primary sequence identity with Sec14p, is nonfunctional as a Sec14p in vivo or in vitro. Yet, SFH proteins sharing low primary sequence similarity with Sec14p (i.e., Sfh2p, Sfh3p, Sfh4p, and Sfh5p) represent novel phosphatidylinositol transfer proteins (PITPs) that exhibit phosphatidylinositol- but not phosyhatidylcholine-transfer activity in vitro. Moreover, increased expression of Sfh2p, Sfh4p, or Sfh5p rescues sec14-associated growth and secretory defects in a phospholipase D (PLD)-sensitive manner. Several independent lines of evidence further demonstrate that SFH PITPs are collectively required for efficient activation of PLD in vegetative cells. These include a collective requirement fur SFH proteins in Sec14p-independent cell growth and in optimal activation of PLD in Sec14p-deficient cells. Consistent with these findings, Sfh2p colocalizes with PLD in endosomal compartments. The data indicate that SFH gene products cooperate with "bypass-Sec14p" mutations and PLD in a complex interaction through which yeast can adapt to loss of the essential function of Sec14p. These findings expand the physiological repertoire of PITP function in yeast and provide the first in vivo demonstration of a role for specific PITPs in stimulating activation of PLD.